Conventional valve actuators, such as those used in aircraft, e.g. to control components on wings, consist of a brushed DC motor that drives a 90° valve via a gear reduction assembly. The position of the valve is simply controlled by a combination of command signals and mechanically-actuated microswitches on adjustable plates actuated by a cam. The rate at which the valve opens and closes is uncontrolled and varies depending on the load and voltage supplied. This sometimes means that the rate can vary over ten times the expected rate.
Another disadvantage of such a conventional actuator is that it can only move the valve between two states: open and closed, with no means of providing intermediate states. The controllers of some current actuators use discrete position sensors to determine the position of the valve. Such actuators require manual calibration before initial use and conventional designs are non-modular. Microswitches require manual adjustment upon assembly and are difficult to set accurately and consistently. Such actuators are also prone to hysteresis and problems due to the backlash/water hammer effect, which can occur when there is a pressure surge or wave resulting when a fluid in motion is forced to stop or change direction suddenly (momentum change). Further, existing actuator technology can also have issues in terms of false indication and wear, e.g. brush wear and loss of accuracy introduced by carbon dust.